If you take exactly one rule away from this entire grammar guide, take this one: in a French conditional sentence, the si-clause never contains a futur. Not in any tier of the conditional system. Not when the sentence refers to tomorrow. Not when English uses the future ("If you will come..." — already wrong in English, but tempting). Not under any circumstance where si means "if." The futur appears in the main clause, the consequence, the thing that happens as a result of the condition — never inside the si-clause itself.
This is the single most stubborn error English speakers (and even native French children) carry around for years. This page exists to drill it into permanent reflex. We will look at why French is so categorical about it, the three-tier system that makes the prohibition watertight, the one genuine exception (when si means "whether"), and the mnemonic French children learn at school.
The rule, in one sentence
When si means "if," the si-clause never contains a futur or a conditionnel. The verb form inside si is always present, imparfait, or plus-que-parfait — depending on the type of conditional.
That is the whole rule. It is shorter than the rules in English, where you also do not say "If you will come" but most learners cannot articulate why.
The Type 1 conditional: real, possible, future-oriented
Type 1 covers conditional sentences where the speaker treats the condition as genuinely possible — even probable. The si-clause is in the présent; the main clause is in the futur simple, or sometimes the présent or impératif.
| Si-clause | Main clause | Reading |
|---|---|---|
| présent | futur simple | If X happens, Y will happen. |
| présent | présent | If X happens, Y happens. (general truth) |
| présent | impératif | If X happens, do Y. |
Si tu viens demain, je serai content.
If you come tomorrow, I'll be happy.
Si j'ai le temps cet après-midi, je passerai à la pharmacie.
If I have time this afternoon, I'll stop by the pharmacy.
Si Lucas appelle pendant que je suis sortie, dis-lui de me rappeler ce soir.
If Lucas calls while I'm out, tell him to call me back tonight.
Si on chauffe l'eau à cent degrés, elle bout.
If you heat water to a hundred degrees, it boils. (general truth — present in both clauses)
Look closely at the first example. The action viens refers to the future — tomorrow. In English we render it as "If you come tomorrow," with what looks like a present-tense verb. French does exactly the same thing: si tu viens demain. The futur appears only in the main clause: je serai content. The si-clause stays in the present even though we are unmistakably talking about tomorrow.
This is the moment most English speakers' grammar instincts misfire. The next page they want to write is si tu viendras demain — using the futur because the time reference is future. That sentence is wrong in French, full stop. There is no register, no dialect, no formal context in which si tu viendras is correct when si means "if."
Why French is so strict about this
The logic is older than French itself. Romance languages inherited a strong conceptual division between realis (the realm of facts and probabilities) and irrealis (the realm of hypotheses and counterfactuals). Inside a si-clause, French marks how confident the speaker is about the condition by choosing one of three tense pairs — and those tense pairs are mutually exclusive. The futur and the conditionnel both belong to the main clause, where the consequence lives; they have no role in expressing the condition itself.
Compare with Italian (se vieni domani, sarò contento), Spanish (si vienes mañana, estaré contento), and Portuguese (se vieres amanhã, ficarei contente). Every Romance language preserves the same prohibition: the verb in the si/se clause cannot be a future or a conditional. French is simply continuing the family tradition. The reason most English-speaking learners struggle is that English uses bare modal-less verbs in this slot ("if you come"), so we never had to think about the rule consciously — and when we try to translate "if you will come" mechanically, French's stricter system flags the futur as ungrammatical.
The three-tier system: a wider view
The futur-prohibition only makes sense in the context of the full conditional system. French has three standard tense pairings, each marking a different stance toward the condition.
| Type | Si-clause | Main clause | Reading |
|---|---|---|---|
| Type 1: real / likely | présent | futur simple (or présent / impératif) | If X happens, Y will happen. |
| Type 2: hypothetical / counterfactual present | imparfait | conditionnel présent | If X were the case, Y would be the case (but it isn't). |
| Type 3: counterfactual past | plus-que-parfait | conditionnel passé | If X had been the case, Y would have been the case (but it wasn't). |
Notice that the futur and the conditionnel — present and past — only ever appear on the right side of the table. The left side, the si-clause, only ever shows présent, imparfait, or plus-que-parfait. There is no row in which the futur or the conditionnel appears on the left.
Si tu viens demain, je serai content.
If you come tomorrow, I'll be happy. (Type 1 — speaker thinks you might actually come.)
Si tu venais demain, je serais content.
If you came tomorrow, I'd be happy. (Type 2 — more hypothetical, less expected.)
Si tu étais venu hier, j'aurais été content.
If you'd come yesterday, I'd have been happy. (Type 3 — counterfactual: you didn't come.)
The mnemonic French schoolchildren learn
French elementary teachers correct si j'aurais and si tu viendras often enough that there is a school-yard rhyme designed to lock the rule in:
Les si n'aiment pas les -rais / -rait / -rions / -rai / -ras / -ra. ("The si's don't like the -rai / -rais endings.")
That is: anything ending in -rai or -rais (i.e., a futur or a conditionnel form) is forbidden right after si. If you find yourself writing je viendrai, tu viendras, il viendra, je viendrais, tu viendrais, il viendrait — and the previous word is si — your sentence is broken.
The rhyme is genuinely useful. As you write or speak, listen for the -rai / -rais sound after si, and treat it as a warning bell. Either reach for the present (Type 1: si tu viens) or for the imparfait (Type 2: si tu venais).
Drill: same English sentence, three French answers
The fastest way to internalize the rule is to take the same English condition and translate it into all three French tiers. Each tier expresses a different stance.
| Tier | French | Stance |
|---|---|---|
| Type 1 | Si tu viens à la fête, je te présenterai à mes parents. | You probably will come. |
| Type 2 | Si tu venais à la fête, je te présenterais à mes parents. | I'm imagining you coming — less expected. |
| Type 3 | Si tu étais venu à la fête, je t'aurais présenté à mes parents. | You didn't come; this is regret about the past. |
In none of the three rows does si take a futur or a conditionnel. The verbs in the si-clause are viens (présent), venais (imparfait), étais venu (plus-que-parfait). The futur and conditionnel show up only in the right-hand column.
Si je gagne au loto, j'achèterai une maison à Marseille.
If I win the lottery, I'll buy a house in Marseille. (Type 1.)
Si je gagnais au loto, j'achèterais une maison à Marseille.
If I won the lottery, I'd buy a house in Marseille. (Type 2.)
Si j'avais gagné au loto, j'aurais acheté une maison à Marseille.
If I had won the lottery, I'd have bought a house in Marseille. (Type 3.)
More drill: real, future-referring sentences
The hardest cases for English speakers are Type 1 sentences where the time reference is unambiguously future. Run through these slowly. In every one, the si-clause is in the présent and the main clause carries the futur.
Si tu finis tes devoirs avant huit heures, on regardera un film.
If you finish your homework before eight, we'll watch a movie.
Si elle me répond avant la fin de la semaine, je lui enverrai le contrat.
If she answers me before the end of the week, I'll send her the contract.
Si tu trouves mon parapluie dans le bus, ramène-le-moi !
If you find my umbrella on the bus, bring it back to me! (présent + impératif — also Type 1)
Si on rate le train de huit heures, on prendra le suivant.
If we miss the eight o'clock train, we'll take the next one.
Si vous arrivez en retard, le serveur ne pourra pas vous garder la table.
If you arrive late, the waiter won't be able to keep the table for you.
In each case, an English-speaking learner has to consciously suppress the urge to write si tu finiras, si elle me répondra, si tu trouveras, si on ratera, si vous arriverez. None of those are French.
The exception: si meaning "whether"
There is exactly one grammatical context where si legitimately takes a futur: when si introduces an indirect question and means "whether." This is not a conditional construction at all — it is a noun-clause construction reporting a question.
Je ne sais pas s'il viendra.
I don't know whether he'll come. (Indirect question — futur is fine.)
Demande-lui si elle pourra venir samedi.
Ask her whether she'll be able to come on Saturday.
Je me demande si elle aura le temps.
I wonder whether she'll have time.
How can you tell the two si's apart? Three reliable tests:
- Substitute "whether." If the English version reads naturally as "I don't know whether he'll come," it is the indirect-question si, and the futur is fine. If it has to be "if" — and the sentence is conditional — the futur is banned.
- Look at the main verb. Indirect-question si always follows verbs of asking, knowing, wondering, doubting: demander, savoir, se demander, douter, ignorer. The si is the object of that verb, not a conditional connector.
- Try inverting the clauses. A conditional si-clause can move to the start of the sentence: Si tu viens, je serai content ↔ Je serai content si tu viens. An indirect-question si-clause cannot: Je ne sais pas s'il viendra cannot become S'il viendra, je ne sais pas.
This exception trips up advanced learners who hear je ne sais pas s'il viendra and think they have caught a French native breaking the rule. They have not. Different si, different rules.
❌ Si tu viendras, je serai content.
Wrong: this is conditional si — futur banned.
✅ Je ne sais pas si tu viendras.
Correct: this is whether-si in an indirect question — futur fine.
What about quand and lorsque?
A second source of confusion: quand and lorsque ("when") follow the opposite rule from si. After quand / lorsque referring to a future event, French uses the futur simple, exactly where English uses the present.
| French | English |
|---|---|
| Si tu arrives demain, ... | If you arrive tomorrow, ... |
| Quand tu arriveras demain, ... | When you arrive tomorrow, ... |
The English rule "after if and when use the present" simply does not transfer to French. Si takes the present (for Type 1); quand takes the futur. Stay alert: quand triggers the futur whenever the time reference is future.
Quand tu arriveras à Paris, envoie-moi un message.
When you get to Paris, send me a message. (quand + futur, not present.)
Si tu arrives à Paris demain, envoie-moi un message.
If you get to Paris tomorrow, send me a message. (si + present, not futur.)
These two sentences differ by a single word but trigger opposite tense rules. Quand says "you will arrive — I just need to know when"; si says "I'm not sure whether you'll arrive."
Common Mistakes
Mistake 1: Putting the futur after si because the time reference is future.
❌ Si tu viendras à la fête, je serai content.
Wrong: si conditional never takes the futur, even when the action is in the future.
✅ Si tu viens à la fête, je serai content.
If you come to the party, I'll be happy.
Mistake 2: Putting the conditionnel after si.
❌ Si j'aurais le temps, je viendrais avec toi.
Wrong: this is the schoolboy mistake. Si never takes the conditional. The Type 2 form is si j'avais.
✅ Si j'avais le temps, je viendrais avec toi.
If I had time, I'd come with you.
Mistake 3: Mixing up si and quand tense rules.
❌ Quand tu arrives à la gare, je viendrai te chercher.
Wrong: quand referring to the future takes the futur, not the present.
✅ Quand tu arriveras à la gare, je viendrai te chercher.
When you get to the station, I'll come pick you up.
Mistake 4: Treating the indirect-question si like a conditional si.
❌ Je ne sais pas si tu viens demain.
Possible but ambiguous — sounds like a Type 1 conditional fragment. For an indirect question, the futur is clearer.
✅ Je ne sais pas si tu viendras demain.
I don't know whether you'll come tomorrow.
Mistake 5: Putting the futur in the si-clause to match the futur in the main clause.
❌ Si on ira au concert, on prendra un taxi.
Wrong: even when both clauses refer to the future, the si-clause stays in the present.
✅ Si on va au concert, on prendra un taxi.
If we go to the concert, we'll take a taxi.
Mistake 6: Translating "if you would" word-for-word.
❌ Si tu voudrais venir, on serait ravis.
Wrong: even though English says 'if you would like,' French doesn't allow the conditional after si. Use the imparfait voulais.
✅ Si tu voulais venir, on serait ravis.
If you'd like to come, we'd be delighted.
Key takeaways
- Si meaning "if" never takes the futur or the conditionnel. The verb inside the si-clause is présent (Type 1), imparfait (Type 2), or plus-que-parfait (Type 3).
- The futur and conditionnel live exclusively in the main clause — the consequence — never in the condition itself.
- Even when the time reference is unambiguously future (si tu viens demain), the si-clause stays in the present.
- The school mnemonic — les si n'aiment pas les -rai / -rais — catches every wrong form by ear.
- The one exception is si meaning "whether" in indirect questions (je ne sais pas s'il viendra) — different si, different rules.
- Quand / lorsque follows the opposite rule: futur with future time reference, where English uses the present.
Now practice French
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Start learning French→Related Topics
- Le Futur: OverviewA1 — French has two main futures — the synthetic futur simple (je parlerai) and the analytic futur proche (je vais parler) — plus the futur antérieur (j'aurai parlé) for completed future actions. This page maps how each is built, when each is used, and how they divide up the future-time space.
- Le Conditionnel: Overview of the French Conditional MoodA2 — The conditionnel is more than 'would' — it's the polite voice, the hypothetical voice, the future-in-the-past, and the journalistic hedge. One paradigm, six everyday jobs, and a place at the heart of grown-up French.
- Le Conditionnel in Si-Clauses: Type 2, Type 3, and Mixed ConditionalsB1 — How the conditionnel pairs with the imparfait and plus-que-parfait to express counterfactual hypotheses about the present and the past — plus the mixed pattern, the universal English-speaker error to avoid, and the schoolyard rhyme that locks the rule in.
- L'Imparfait in Si-Clauses: Hypotheticals, Suggestions, and WishesB1 — How the imparfait pairs with the conditional to express counterfactual hypotheses, and how 'si + imparfait' alone proposes plans, regrets, and wishes.
- Le Conditionnel Présent: Formation et TerminaisonsA2 — How to build the conditionnel for any French verb — futur stem plus imparfait endings. The rule is one line; the pronunciation distinction with the futur (je serai vs je serais) is the trap.